xfs: cross-reference reverse-mapping btree

When scrubbing various btrees, we should cross-reference the records
with the reverse mapping btree and ensure that traversing the btree
finds the same number of blocks that the rmapbt thinks are owned by
that btree.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/scrub/common.h

@@ -148,6 +148,10 @@ int xfs_scrub_walk_agfl(struct xfs_scrub_context *sc,
 			int (*fn)(struct xfs_scrub_context *, xfs_agblock_t bno,
 				  void *),
 			void *priv);
+int xfs_scrub_count_rmap_ownedby_ag(struct xfs_scrub_context *sc,
+				    struct xfs_btree_cur *cur,
+				    struct xfs_owner_info *oinfo,
+				    xfs_filblks_t *blocks);
 
 int xfs_scrub_setup_ag_btree(struct xfs_scrub_context *sc,
 			     struct xfs_inode *ip, bool force_log);